earth science

Paramelaconite

Paramelaconite is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Paramelaconite rather than just read about it. In short: Paramelaconite is a rare, black-colored copper(I,II) oxide mineral with formula CuI2CuII2O3 (or Cu4O3). It was discovered in the Copper Queen Mine in Bisbee, Arizona, about 1890.

Key takeaways

Paramelaconite belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Paramelaconite to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Paramelaconite from memory before moving on to harder problems.

Reference excerpt

Paramelaconite is a rare, black-colored copper(I,II) oxide mineral with formula CuI2CuII2O3 (or Cu4O3). It was discovered in the Copper Queen Mine in Bisbee, Arizona, about 1890. It was described in 1892 and more fully in 1941. Its name is derived from the Greek word for "near" and the similar mineral melaconite, now known as tenorite.

Description and occurrence

Paramelaconite is black to black with a slight purple tint in color, and is white with a pinkish brown tint in reflected light. The mineral occurs with massive habit or as crystals up to 7.5 cm (3 in). A yellow color is formed when the mineral is dissolved in hydrochloric acid, a blue color when dissolved in nitric acid, and a slightly brown precipitate when exposed to ammonium hydroxide. When heated, paramelaconite breaks down into a mixture of tenorite and cuprite. Paramelaconite is a very rare mineral; many specimens purported as such are in fact mixtures of cuprite and tenorite. Paramelaconite forms as a secondary mineral in hydrothermal deposits of copper. It occurs in association with atacamite, chrysocolla, connellite, cuprite, dioptase, goethite, malachite, plancheite, and tenorite. The mineral has been found in Cyprus, the United Kingdom, and the United States.

Structure Paramelaconite crystallizes in the tetragonal crystal system. Its space group was correctly identified by Frondel as I41/amd. In 1978, O'Keeffe and Bovin determined the formula to be Cu4O3, specifically CuI2CuII2O3. There has been misunderstanding and misreporting of the mineral's crystal structure, due in part to a typographical error in O'Keeffe and Bovin's paper and the commonality of choosing an incorrect origin for the I41/amd space group. At the same time as O'Keeffe and Bovin's report, a paper by Datta and Jeffery determined a structure for the mineral based on the incorrect formula CuII12CuI4O14. The formula originated from incorrectly assuming that Frondel's analysis was of a homogeneous crystal of paramelaconite.

Synthesis The synthesis of microscopic paramelaconite was reported in 1986 as a product of the decomposition of CuO in an electron microscope. However, this method is not easily scaled up to produce samples large enough for study. Reduction of CuO and decomposition in a vacuum and controlled oxidation of Cu2O failed to synthesize the mineral. Experiments at the National Bureau of Standards using aqueous solutions up to 250 °C produced only Cu2O and CuO. Oxidation of copper or its alloys also does not produce paramelaconite, despite reports to the contrary. The first unequivocal synthesis of the mineral was achieved in the 1990s and published in 1996. The material produced was 35% Cu4O3, 27% Cu2O, and 38% CuO. The process consists of the leaching of copper or its oxides with concentrated aqueous ammonia in a Soxhlet extractor. The reaction forms a deep blue complex of cupric ammonium that is converted to a residue of black oxide in the apparatus.

History

Albert E. Foote visited the Copper Queen Mine about 1890, where he obtained two specimens containing unknown minerals. He could only associate them with anatase, but he thought it unlikely that the minerals were any form of titanium oxide. The specimens were sold to Clarence M. Bement at fifty dollars apiece, and with his permission, were studied by George Augustus Koenig. Bement's collection, including the specimens of paramelaconite, were purchased by J. P. Morgan in 1900 and given to the American Museum of Natural History. Owing to its unique appearance, Koenig assigned the mineral as a new species. His description of the mineral appeared in an 1892 publication of the Academy of Natural Sciences of Philadelphia. He named the mineral paramelaconite from the Greek παρά, meaning "near", and the mineral melaconite (now known as tenorite), for its compositional similarity to melaconite. At the time, however, the mineral was not recognized as a valid species. Clifford Frondel studied the mineral in more detail and published his results in the journal American Mineralogist in 1941. When the International Mineralogical Association was founded in 1959, paramelaconite was grandfathered as a valid mineral species. In the early 1960s, the third known specimen of paramelaconite was discovered from the Copper Queen Mine; Koenig donated it to the A. E. Seaman Mineral Museum. Other specimens in the museum, labeled as originating from the Algomah Mine in Ontonagon County, Michigan, were also found to contain paramelaconite. The type material is held at the A. E. Seaman Mineral Museum in Houghton, Michigan, the American Museum of Natural History in New York City, Harvard University in Cambridge, Massachusetts, the National Museum of Natural History in Washington, D.C., and the Natural History Museum in London.

References

Bibliography Datta, N.; Jeffery, J. W. (1978). "The Crystal Structure of Paramelaconite, Cu2+12Cu1+4O14". Acta Crystallographica Section B. 34: 22–26. doi:10.1107/S056774087800223X. (subscription required) Frondel, Clifford (November 1941). "Paramelaconite, a tetragonal oxide of copper" (PDF). American Mineralogist. 26 (11): 567–672. Koenig, George Augustus (1892). "On paramelaconite, and the associated minerals". Proceedings of the Academy of Natural Sciences of Philadelphia. 43: 284–291. Morgan, P. E. D.; Partin, D. E.; Chamberland, B. L.; O'Keeffe, M. (January 5, 1996). "Synthesis of Paramelaconite: Cu4O3". Journal of Solid State Chemistry. 121 (1): 33–37. Bibcode:1996JSSCh.121...33M. doi:10.1006/jssc.1996.0005. (subscription required) O'Keeffe, M.; Bovin, J.-O. (January–February 1978). "The crystal structure of paramelaconite Cu4O3" (PDF). American Mineralogist. 63 (12): 180–185. Williams, Sidney A. (May–June 1962). "Paramelaconite and associated minerals from the Algomah mine, Ontonagon County, Michigan" (PDF). American Mineralogist. 47 (5–6): 778–779.

Further reading Pinsard-Gaudart, L.; Rodríguez-Carvajal, J.; Gukasov, A.; Monod, P. (1 March 2004). "Magnetic properties of paramelaconite (Cu4O3): A pyrochlore lattice with S = 1/2". Physical Review B. 69 (10) 104408. Bibcode:2004PhRvB..69j4408P. doi:10.1103/PhysRevB.69.104408. (subscription required)

External links Media related to Paramelaconite at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Paramelaconite

Start with the simplest possible case. Write down what Paramelaconite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Paramelaconite before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Paramelaconite ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Paramelaconite

In research: Paramelaconite appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Paramelaconite in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Paramelaconite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Copper(I,II) minerals, Minerals described in 1892, Minerals in space group 141, so understanding it makes those chapters shorter.
In everyday life: Look for Paramelaconite outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Paramelaconite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Paramelaconite means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Paramelaconite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Paramelaconite in simple terms?

Paramelaconite is a rare, black-colored copper(I,II) oxide mineral with formula CuI2CuII2O3 (or Cu4O3). It was discovered in the Copper Queen Mine in Bisbee, Arizona, about 1890.

Why does Paramelaconite matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Paramelaconite?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Paramelaconite.